Subacute Sclerosing Panencephalitis

To the Editor:— The report states that there were three differences from the study by Katz et al. Transmission of an encephalitogenic agent was not possible. Much higher serum measles antibody titers were observed. There were only type B nucleiform inclusions in our patients. These observations have now been extended to four other patients. We would point out that the variation in clinical onset, stages, duration of SSPE, the immune responses in the patients, and the intensity of the measles virus infection in the brain may result in the differences in serum measles antibody titers, the pathological features, and the success or failure to transmit the agent to ferrets or monkeys. Furthermore, differences in antibody titers between laboratories may be due to the techniques employed. A thorough search for other inclusions in two other biopsy specimens from SSPE patients, as well as a review of the previous